Does this mod do anything with EntityPlayer.isWet() method?
I have a mod using this method to do some magic.But if I using my mod and ToughAsNails together ,isWet() will ignore raining but still work in water .
And even enderman wouldn't damage in rain.

Yes. It seems to be broken due to one of our ASM overrides. There is another issue for this though, so I'm closing this one.